Vacuum tube with replacement filaments



April 3, 1956 G, 1 HOOPER 2,740,916

VACUUM TUBE WITH REPLACEMENT FILAMENTS Filed sept. 1, 1954 vllllllllllllm GABA/fe J. #00P/5e IN VEN TOR.

VACUUM TUBE WITH REPLACEMENT FILAMENTS y Garner J. Hooper, El Paso, Tex. y Application September 1, 1954, Serial No. 453,617v 2 Claims. (Cl. 313-270) This invention relates to vacuum tubes, and more par ticularly to a vacuum tube, such as a cathode ray tube,

having a replaceable heater filament.

ment, the tube employing substantially a conventional' base, whereby it may be employed with the usual-'type of tube socket, the base being inexpensive to fabricate, beingrugged in construction, and being arranged so that the filament element maybe readily removed from the socket and replaced 'with a new, filament element whenever required.

A still further object of the invention is to provide an improved cathode ray tube, for example, a cathode ray tube for use withl a television receiver, the tube being provided with a replaceable filament element enabling the filament to be easily replaced whenever necessary, thereby eliminating the necessity of replacing the entire cathode ray tube, the improved replaceable filament structure being suitable for use with any type of cathode ray tube employing a heater filament and cathode, and enabling a cathode ray tube to be used for an indefinite period of time, since the filament thereof may be easily and inexpensively replaced.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure l is a side elevational view of a cathode ray tube constructed in accordance with the present invention and provided with a replaceable heater filament, the neck portion of the tube being partly broken away and being partly in cross section to reveal the interior constructional details thereof.

Figure 2 is an enlarged side elevational view, partly in cross section, of the hollow cathode member employed in the tube of Figure l.

Patented Apr. 3, 1956 such as a screen, a first anode, a second anode, and the like.

The bulb 12 has the reduced .neck portion 14 and the pronged terminal base 15 secured on said neck portion, said base 15 having the usual terminal prongs 16 and being formed with the center ribbed key member 17. Designated generally at 18 is a tubular hollow cathode member which extends axially through the key member 17, as shown, the cathode member extending axially into the reduced neck portion 14 and being provided at its inner end with the electron emitting member 19 which is sealingly secured on the inner end of the cathode 18.

As shown in Figures 2 and 3, the cathode 18 comprises,

an inner metallic sleeve element 20, an outer metallic sleeve element 21 and an intermediate sleeve element 22 of glass or other suitable heat insulating material which is sealingly securedl on the adjacent end portions of the metallic sleeve members 21 and 20 and which axially connects said sleeve elements together.

As shown in Figure 2, the glass sleeve 22 supports the ends of the metallic sleeve elements 20 and 21 in spaced relationship and acts as a heat insulator, substantially preventing the rapid transmission of heat from the inner metallic sleeve 20 to the outer metallic sleeve 21, and thus preventing heat from being conducted away rapidly from the inner sleeve element 20.

As shown in Figure l, the end of the reduced neck portion 14 is sealingly secured on the intermediate heat insulating sleeve element 22 of the cathode 18, whereby the interior of the vacuum tube may be evacuated and may be hermetically sealed in any suitable manner 'and is sealed with respect tothe interior of the hollow cathode 18.`

As shown in Figure 2, the electron-emitting cap element 19 is sealingly secured on the inner end of the metallic sleeve element 20.

Figure 3 is a vertical cross sectional view taken through the removable cap member employed on the cathode of Figure 2 and showing the filament member carried by said cap member and further showing the porcelain spacer elements supporting the filament member, said spacer elements being shown partly in cross section.

Referring to the drawings, 11 generally designates an improved vacuum tube constructed in accordance with the present invention, for example, a cathode ray tube of a type suitable for use in television receivers. The tube 11 comprises a bulb 12 provided with a viewing face 13, said face having a suitable fluorescent inside coating, as in a conventional television picture tube, and being also provided with the other conventional internal elements of glass or other suitable insulating material. Extendingv through and sealingly secured in the end wall element 25 are the parallel, spaced filament-supporting rods 26 which project externally from the wall element 25, as is clearly shown in Figures l to 3, defining terminals for the heater filament of cathode 18. Connected between the inner ends of the conductive rods 26 is the heater filament 27, the filament 27 being normally supported closely adjacent to the electron-emitting cap member 19, whereby the cap member 19 is heated to its specified temperature when the filament element 27 is energized.

The filament-supporting rods 26 extend through and are secured in a plurality of circular spacer members 28 of porcelain, or other suitable insulating material which are slidably received inside the respective sleeve elements 21 and 20, as shown in Figure 2, said members 28 acting as centering means for the heating filament 27.

The cap member 24 is provided with the laterally projecting evacuation tube 29 of soft metal or the like, adapted tuA1 be connected to a vacuum pump for evacuating the interior of the hollow cathode 18 after a replacement filament has been installed therein. The evacuation tube 29 is provided with the lug or screw closure cap 30 which is threadedly engaged in the end of the evacuation tube 29 and which is employed as an additional means for sealing the evacuation tube after said tube has been mechanically crimped or otherwise deformed to provide an initial seal for the hollow cathode 13.

As shown in Figure 1, the cap 24 is non-circular in cross section, for example, hexagonal, whereby it may be readily engaged by a wrench or other similar implement. When a filament burns out, the cap member 24 is loosened, and is unscrewed from the end of the metal sleeve element 21,

t) after which the cap member and the filament-supporting assembly including the rods 26 and spacers 28, may be withdrawn from the hollow cathode 18. A new filamentsupporting assembly, including a cap member 24, lilamentsupporting rods 26, a filament element 27 and Spacer elements 28, as shown in Figure 3 may then be inserted in the hollow cathode i8, after which the cap member 24 is screwed on to the end of the metallic sleeve element 21, as shown in Figure 2. The end plug 30 is then removed from the tube 29 and said tube is connected to a vacuum pump, whereby the interior of the hollow cathode 1S may be then exhausted.

After the desired vacuum has been provided inside the hollow cathode 13, the soft metal tube 29 is crimped at its intermediate portion, as shown at 31 in Figure 1,' to seal the tube 29, and to thus seal ott the interior of the. hollow cathode 18. The tube 29 may then be disconnected from the vacuum pump and the plug 30 may then. be engaged in the end of tube 29 to provide an additional seal for said tube 29.

From the above it will be apparent that whenever afilamentv burns out, said iilament may be readily replaced, Without the necessity of replacing the entire tube 11, it being, only necessary to remove the burnt-out filament and replace same with a new filament in the manner above described. Thus, no special tools are required except for an inexpensive vacuum pump, and there would be no necessity of shipping the entire tube back, to the factory for replacement.

The deformation or crimping of the soft metal tube 29 may be accomplished by any suitable implement capable of pressingl the walls of the soft metal tube 29 together to provide the desired seal.

It will be readily understood that after a new filament is installed, the filament chamber, namely, the interior of the hollow cathode 18 must be evacuated prior tor the energization of the lilament element 27 and the heating of the cathode.

While a specific embodiment of an improvement vacuum tube having a replaceable filament has been disclosed in the foregoing description, it will be understoodthatvarious modifications within the spirit of the invention may occur to. those skilled in the art. Therefore it is intended that no limitations be placed on the invention except as defined bythe scope of the appended claims.

What is claimed is:

1. A bulb having a reduced neck portion, a pronged terminal base secured on saidneck portion, a tubular hollow cathode member extending through said base into said neck portion, said cathode member comprising an outer metallic sleeve element and an inner metallic sleeve element connected together by a sleeve of heat insulating material, a cap member detachabl'y and sealingly secured on the outer end of said cathode member, a heater filament carried by said cap member, said filament extending into and adjacent said cathode member in heat-transmitting relation thereto and having terminal ends projecting externally of said` cap member, and a relatively thin walled air evacuation conduit connected to said cap member, the walls of said conduit being adapted to. be pressed together to seal the cap member after said cathode member has been evacuated.

2. A bulb having a reduced neck portion, a pronged terminal base secured on said neck portion,l a tubular hollow cathode member extending through said base into said neck portion, said cathode member comprisingl an inner capped metallic sleeve element, an outer metallic sleeve element, and an intermediate sleeve of heat-insulating. material connectingsaid metallic sleeve elements, a cap member threadedly and sealingly engaged on the outer end of said outer metallic sleeve element, a heater filament carried by said cap member, said filament extending into and adjacent said. inner capped metallic sleeveV element in heat-transmitting relation thereto and having terminal ends projecting externally of said cap member,and a relatively thin walled air evacuation conduit connected to said cap member, the walls of said conduit being adapted to be pressed together to seal the cap member after said cathode member has been evacuated.

References Cited in the file. of this patent UNITED STATES PATENTS 1,368,584 Torrisi Feb. 15, 1921 1,644,796l Stuart Oct. 1l, 1927 1,965,849 Mcllvaine July l0, 1934 21,948,129 Loughbridge July 2l, 1936 2,372,037- Watrous, Jr Mar. 20, 1945 2,637,005 Hood II et al Apr. 28, 1953 

